Use only Span{} constructor for byte-like types where possible

This removes bloat that is not needed.

src/net.cpp

@@ -2939,13 +2939,13 @@ void CaptureMessageToFile(const CAddress& addr,
     AutoFile f{fsbridge::fopen(path, "ab")};
 
     ser_writedata64(f, now.count());
-    f.write(MakeByteSpan(msg_type));
+    f << Span{msg_type};
     for (auto i = msg_type.length(); i < CMessageHeader::COMMAND_SIZE; ++i) {
         f << uint8_t{'\0'};
     }
     uint32_t size = data.size();
     ser_writedata32(f, size);
-    f.write(AsBytes(data));
+    f << data;
 }
 
 std::function<void(const CAddress& addr,